Formulations including a 1, 3-dicarbonyl compound chelating agent for stripping residues from semiconductor substrates

ABSTRACT

A semiconductor wafer cleaning formulation for use in post plasma ashing semiconductor fabrication comprising the following components in the percentage by weight ranges shown: an organic amine 2-98%; water 0-50%; a 1,3-dicarbonyl compound chelating agent 0.1-60%; a second or alternative chelating agent 0-25%; a polar organic solvent 2-98%.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the U.S. National Phase application to Internationalapplication No. PCT/US97/23917, which claims priority to U.S.Provisional Application Ser. No. 60/044,826, filed Apr. 25, 1997 andU.S. Provisional Application Ser. No. 60/034,144, filed Dec. 24, 1996.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to chemical formulations used insemiconductor wafer fabrication and particularly to chemicalformulations that are utilized to remove residue from wafers following aresist plasma ashing step.

2. Description of the Prior Art

The prior art teaches the utilization of various chemical formulationsto remove residue and clean wafers following a resist ashing step. Someof these prior art chemical formulations include akaline compositionscontaining amines and/or tetraalkyl ammonium hydroxides, water and/orother solvents, and chelating agents. The various prior art formulationshave drawbacks which include unwanted removal of metal or insulatorlayers and the corrosion of desirable metal layers, particularlyaluminum and aluminum-copper alloys and titanium nitride features. Thereis therefore a need for chemical formulations which effectively removeresidue following a resist ashing step which do not attack andpotentially degrade delicate structures which are meant to remain on awafer.

SUMMARY OF THE INVENTION

A semiconductor wafer cleaning formulation for use in post plasma ashingsemiconductor fabrication comprising the following components in thepercentage by weight ranges shown:

An organic amine 2-98% Water 0-50% A 1,3-dicarbonyl compound chelatingagent 0.1-60%   A second or alternative chelating agent 0-25% A polarorganic solvent 2-98%

It is an advantage of the present invention that it effectively removesinorganic residues following a plasma ashing step.

It is another advantage of the present invention that it effectivelyremoves metal halide and metal oxide residues following plasma ashing.

These and other features and advantages of the present invention willbecome understood to those of ordinary skill in the art upon review ofthe following detailed description of the preferred embodiments.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention comprises formulations that are suitable forstripping inorganic wafer residues which originate from high densityplasma etching followed by ashing with oxygen-containing plasmas.

The formulations contain 1, 3-dicarbonyl compounds and/or other metalchelating agents, amines, and water or another solvent as primaryingredients.

The preferred formulations utilize the following components (percentagesare by weight):

An organic amine 2-98% Water 0-50% A 1,3-dicarbonyl compound chelatingagent 0.1-60%   A second or alternative chelating agent 0-25% A polarorganic solvent 2-98%

The preferred amines are:

Pentamethyldiethylenetriamine (PMDETA) 5-95% Triethanolamine (TEA) 5-95%

Other amines that are effective are:

Diazabicyclo (2.2.2) octane

Diethylenetriaamine

3,3′-Iminobis (N,N-dimethylpropylamine)

N-Methylimidazole

Tetraethylenepentamine

Triethylenetetramine

Trimethoxyethoxyethylamine

Diethanolamine

Methyldiethanolamine

Tetramethylhexanediamine

N,N-Diethylethanolamine

The preferred 1,3-dicarbonyl compound chelating agents are:

2,4-Pentanedione 2-90%  Methyl acetoacetate 15-70%   Dimethylmalonate10-48.3%

Other 1, 3-dicarbonyl compounds which may be utilized are:

N-Methylacetoacetamide

Acetoacetamide

Malonamide

The preferred solvents are:

Water 0-50% Ethylene glycol 0-74% N-Methylpyrrolidone (NMP) 0-49%Sulfolane 0-10%

The preferred secondary or alternative chelating agents that areutilized in some of the formulations are:

Ammonium pyrrolidinedithiocarbamate 0-25% Ammonium carbamate 0-15%Ammonium oxalate 0-15% Ammonium thiocyanate 0-15% Ammonium thiosulfate0-15% Trifluoroacetic acid 0-12%

The utilization of 1,3-dicarbonyl compounds and/or other metal-chelatingagents in combination with amines and a solvent are unique features ofthe invention. These formulations provided better stripping performanceand less corrosivity than traditional formulations containing catechol,amine, and solvent.

Examples of the preferred formulations are:

PMDETA 40-55% 2,4-Pentanedione 15-20% Water 26.7-45% TEA 40%2,4-Pentanedione 15% Water 45% PMDETA 11.7-40% 2,4-Pentanedione 15-40%Ethylene glycol 45-48.3% PMDETA 11.7% 2,4-Pentanedione 40% NMP 48.3%

The inventors expect that other closely related ingredients would beexpected to show comparable performance to those utilized in thepreferred formulations.

These include:

A. Other tertiary organic amines are expected to be suitable:

B. Other 1,3-dicarbonyl compounds and related compounds are expected todisplay comparable performance. These would have the following generalstructure:

X—CHR—Y in which

R is either a Hydrogen atom or an aliphatic group and

X and Y are functional groups containing multiply bonded moities knownto have electron-withdrawing properties, for example X and Y may beCONH₂ CONHR′, CN, NO₂, SOR′, SO₂Z in which R′ represents an alkyl groupand Z represents another atom or group. X and Y may be identical ordifferent.

C. Other carbamate salts are expected to function similarly to ammoniumcarbamate.

D. Other dialkyldithiocarbamates are expected to function similarly toammonium pyrrolidinedithiocarbamate.

E. Other polar organic solvents are expected to be suitable either aloneor when mixed with water.

F. It would also be expected that inclusion of optional components suchas surfactants, stabilizers, corrosion inhibitors, buffering agents, andcosolvents would constitute obvious additions to those practiced in theart.

The formulations of the present invention are particularly useful onwafers which have been etched with chlorine- or fluorine-containingplasmas followed by oxygen plasma ashing. The residues generated by thistype of processing typically contain inorganic materials such as, butnot limited to aluminum oxide and titanium oxide. These residues areoften difficult to dissolve completely without causing corrosion ofmetal and titanium nitride features required for effective deviceperformance.

Four types of commercially generated wafers containing vias and metallines were evaluated using the formulations of the present invention. Ineach case, following plasma etching and ashing the residue was removedfrom the wafer by immersion of the wafer in a formulation bath at 60° C.for 30 minutes followed by washing with deionized water and drying witha stream of nitrogen gas. It is expected by the inventors that theformulations can also be applied by spraying onto the wafers in anautomated spray tool followed by a water rinse.

The four via and line structures were:

1. 0.8 micron diameter, four layer vias comprised of silicon oxide topand second layers, a third layer of titanium nitride, and a bottom layerof aluminum, silicon, copper (AlSiCu) alloy. The substrate was siliconoxide.

2. One micron diameter, two-layer vias comprised of a top layer ofsilicon oxide (7000 Angs. thick) and a middle layer of titanium nitride(1200 Angs. thick) on top of a silicon substrate.

3. 1.2 micron wide, 4-layer metal lines with a top layer ofTitanium/Tungsten (6000 Angs. thick), a third layer of Titanium/Tungsten(1200 Angs thick), and a bottom layer of Titanium (500 Angs. thick) on asilicon oxide substrate.

4. Two microns wide, 3-layer metal lines with a top layer of Titanium(200 Angs. thick), a middle layer of Aluminum/Silicon/Copper (750 Angs.thick), and a bottom layer of Titanium/Tungsten (1250 Angs. thick) on asilicon oxide substrate.

The present invention formulations were rated for relative strippingeffectiveness and corrosivity. The preferred formulations scored bestand, in overall performance based on both stripping effectiveness andlow corrosivity, are approximately equal.

While the present invention has been described with reference to certainpreferred embodiments, it will be understood by those skilled in the artthat various alterations and modifications may be made therein withoutdeparting from the true spirit and scope of the invention. It istherefore intended that the following claims cover all such alterationsand modifications which nevertheless include the true spirit and scopeof the invention.

What I claim is:
 1. A semiconductor wafer cleaning formulation for usein post plasma ashing semiconductor fabrication comprising the followingcomponents in the percentage by weight ranges shown: An organic amine2-98% Water 0-50% A 1,3-dicarbonyl compound chelating agent 0.1-60% Asecond or alternative chelating agent 0-25% A polar organic solvent2-98%


2. A cleaning formulation as described in claim 1 wherein said organicamine is chosen from the group consisting of:Pentamethyldiethylenetriamine (PMDETA) 5-95% Triethanolamine (TEA)5-95%.


3. A cleaning formulation as described in claim 1 wherein said1,3-dicarbonyl compound chelating agent is chosen from the groupconsisting of: 2,4-Pentanedione  2-90% Methyl acetoacetate 15-70%Dimethylmalonate 10-48.3%.


4. A cleaning formulation as described in claim 1 wherein said polarorganic solvent is chosen from the group consisting of: Ethylene glycol0-74% N-Methylpyrrolodone (NMP) 0-49% Sulfolane 0-10%.


5. A cleaning formulation as described in claim 1 wherein said secondaryor alternative chelating agent is chosen from the group consisting of:Ammonium pyrrolidinedithiocarbamate 0-25% Ammonium carbamate 0-15%Ammonium oxalate 0-15% Ammonium thiocyanate 0-15% Ammonium thiosulfate0-15% Trifluoroacetic acid 0-12%


6. A cleaning formulation as described in claim 1 wherein said organicamine is chosen from the group consisting of:Pentamethyldiethylenetriamine (PMDETA) Triethanolamine (TEA)Diazabicyclo (2.2.2) octane Diethylenetriamine 3,3′-Iminobis(N,N-dimethylpropylamine) N-Methylimidazole TetraethylenepentamineTriethylenetetramine Trimethoxyethoxyethylamine DiethanolamineMethyldiethanolamine Tetramethylhexanediamine N,N-Diethylethanolamine.7. A cleaning formulation as described in claim 1 wherein said1,3-dicarbonyl compound chelating agent is chosen from the groupconsisting of: 2,4-Pentanedione Methyl acetoacetate DimethylmalonateN-Methylacetoacetamide Acetoacetamide Malonamide.
 8. A cleaningformulation as described in claim 1 wherein said organic amine is chosenfrom the group consisting of: Pentamethyldiethylenetriamine (PMDETA)5-95% Triethanolamine (TEA) 5-95%

said 1,3-dicarbonyl compound chelating agent is chosen from the groupconsisting of: 2,4-Pentanedione  2-90% Methyl acetoacetate 15-70%Dimethylmalonate 10-48.3%  

and said polar organic solvent is chosen from the group consisting of:Ethylene glycol 0-74% N-Methylpyrrolodone (NMP) 0-49% Sulfolane  0-10%.


9. A cleaning formulation as described in claim 1 wherein said chelatingagent would have the following general structure: X—CHR—Y in which R iseither a hydrogen atom or an aliphatic group and X and Y are functionalgroups containing multiply bonded moities known to haveelectron-withdrawing properties, wherein X and Y may be CONH₂, CONHR′,CN, NO₂, SOR′, SO₂Z in which R′ represents an alkyl group, and Zrepresents another atom or group. and wherein X and Y may be identicalor different.
 10. A cleaning formulation as described in claim 1 beingcomprised of: PMDETA 40-55% 2,4-Pentanedione 15-20% Water 26.7-45%. 


11. A cleaning formulation as described in claim 1 being comprised of:TEA 40% 2,4-Pentanedione 15% Water  45%.


12. A cleaning formulation as described in claim 1 being comprised of:PMDETA 11.7-40% 2,4-Pentanedione   15-40% Ethylene glycol  45-48.3%.


13. A cleaning formulation as described in claim 1 being comprised of:PMDETA 11.7% 2,4-Pentanedione   40% NMP  48.3%.


14. A method for fabricating a semiconductor wafer including the stepscomprising: plasma etching a metalized layer from a surface of thewafer; plasma ashing a resist from the surface of the wafer followingthe metal etching step; cleaning the wafer in the following step using achemical formulation including the following components in thepercentage by weight ranges shown: An organic amine 2-98% Water 0-50% A1,3-dicarbonyl compound chelating agent 0.1-60% A second or alternativechelating agent 0-25% A polar organic solvent 2-98%


15. A method as described in claim 14 wherein said organic amine ischosen from the group consisting of: Pentamethyldiethylenetriamine(PMDETA) 5-95% Triethanolamine (TEA)  5-95%.


16. A method as described in claim 14 wherein said 1,3-dicarbonylcompound chelating agent is chosen from the group consisting of:2,4-Pentanedione  2-90% Methyl acetoacetate 15-70% Dimethylmalonate10-48.3%. 


17. A method as described in claim 14 wherein said polar organic solventis chosen from the group consisting of: Ethylene glycol 0-74%N-Methylpyrrolodone (NMP) 0-49% Sulfolane  0-10%.


18. A method as described in claim 14 wherein said second or alternativechelating agent is chosen from the group consisting of: Ammoniumpyrrolidinedithiocarbamate 0-25% Ammonium carbamate 0-15% Ammoniumoxalate 0-15% Ammonium thiocyanate 0-15% Ammonium thiosulfate 0-15%Trifluoroacetic acid  0-12%.


19. A method as described in claim 14 wherein said organic amine ischosen from the group consisting of: Pentamethyldiethylenetriamine(PMDETA) Triethanolamine (TEA) Diazabicyclo (2.2.2) octaneDiethylenetriamine 3,3′-Iminobis (N,N-dimethylpropylamine)N-Methylimidazole Tetraethylenepentamine TriethylenetetramineTrimethoxyethoxyethylamine Diethanolamine MethyldiethanolamineTetramethylhexanediamine N,N-Diethylethanolamine.
 20. A method asdescribed in claim 14 wherein said 1,3-dicarbonyl compound chelatingagent is chosen from the group consisting of: 2,4-Pentanedione Methylacetoacetate Dimethylmalonate N-Methylacetoacetamide AcetoacetamideMalonamide.
 21. A method as described in claim 14 wherein said organicamine is chosen from the group consisting of:Pentamethyldiethylenetriamine (PMDETA) 5-95%  Triethanolamine (TEA)5-95%.

said 1,3-dicarbonyl compound chelating agent is chosen from the groupconsisting of: 2,4-Pentanedione  2-90% Methyl acetoacetate 15-70%Dimethylmalonate 10-48.3%  

and said polar organic solvent is chosen from the group consisting of:Ethylene glycol 0-74% N-Methylpyrrolodone (NMP) 0-49% Sulfolane  0-10%.


22. A method as described in claim 14 wherein said chelating agent wouldhave the following general structure: X—CHR—Y in which R is either ahydrogen atom or an aliphatic group and X and Y are functional groupscontaining multiply bonded moities known to have electron-withdrawingproperties, wherein X and Y may be CONH₂, CONHR′, CN, NO₂, SOR′, SO₂Z inwhich R′ represents an alkyl group and Z represents another atom orgroup and wherein X and Y may be identical or different.